Electrical-resistance material.



UNITED STATES PATENT OFFICE.

' CHARLES RUZICKA, 0F GRAVESEND, ENGLAND.

ELECTRICAL-RESISTANCE MATERIAL.

No Drawing.

To all whom it may concern:

Be it known that I, CHARLES RUzIexA, a subject of the Emperor ofAustria, and resident of 9 Woodville Terrace, Gravesend, in the countyof Kent, England, analytical and electro chemist, have invented certamnew and useful Improvements in Electrical- Resistance Materials, ofwhich the following is a specification.

This invention relates to electrical resistance materials made from acomminuted carbid-containing. mixture whose essential ingredients havebeen bound together into a homogeneous mass.

The object of the invention is to provide a hard, compact materialhaving a high melting point which may be repeatedly raised to a hightemperature without detriment to its physical or electrical properties.

According to my invention the resistance material is made from a mixturein the comminuted or pulverulent form of, on the one hand, a carbid of ametal or a carbid of a metalloid (or carbids of a metal or metals orcarbids of a metalloid or metalloids), such metal or metals, metalloidor metalloids, having a comparatively high specific electricalresistance and a melting point above 1500 degrees centigrade; and on theother hand, of a carbid of a metal (or carbids of a-metal or metals),such metal or metals having a relatively lower specificelectrical'resistance and a melting point not above 1500 degreescentigrade and not below 800 degrees centigrade.

Carbids of the first class above mentioned may bedescribed as a compoundof carbon and an element, said element having a melting point over 1500degrees centigrade, and in speaking of such carbids or compounds in thespecification andclaims, I refer specifically to carbids of titanium,chromium,

tungsten, molybdenum, boron or silicon.

Carbids of the second class above mentioned may be described as acompound of carbon and an element, said element having a melting pointnot above 1500 degrees centigrade and not below 800 degrees centigrade,and in speaking of such carbids in the specification and claims, I referspecifically to carbids of manganese, iron, nickel or cobalt. To amixture of these carbids there may be added, in the course ofmanufacturing the resistancematerial, (either forthe purpose of moreeffectively binding the individual particles of the carbids or ofincreasing the Specification of Letters Patent.

Patented Nov. 13, 1917.

Application filed May 16, 1914. Serial No. 838,923.

specific electrical resistance of the product, or of both bindingtogether the individual particles and increasing the electricalresistance) a permanent substance having a melting point below that ofany of the said carbids (e. 9. neutral feldspar, calcium silicate, ironsilicate, or aluminium'borate or a mixture thereof also in thecomminuted or pulverulent form) and which is neutral in respect of theother substances employed and a conductor of the second class.Furthermore, there may be added to the mixture of the carbids in thecourse of manufacturing the resistance material (with or without theaddition of the neutral permanent substance) a temporary binding agent(such as a distilled dense mineral oil, glycerin, distilled mineraljelly) which is neutral and inert with respect to all the otheringredients and of such a nature that it will volatilize or burn awayduring or prior to the heating process, leaving to all intents andpurposes no residue capable of modifying the specific electricalresistance of the product obtained.

The carbids employed may be either full carbids or carbids of a higheror lower degree than the full carbid. In any case care should be takenthat, as the presence of free or unbound carbon would have a detrimentaleffect upon the resistance material under working conditions, no free orunbound carbon, whether from the carbid employed or from any othersource, shall be present in the product.

In carrying out my invention, a powdery mixture of carbids of the twoclasses above referred to ,(with or without the addition of thepermanent inert substance and with or without the addition of a quantityof the temporary binding agent sufficient to bring the mixture to a damppowder or pasty mass) is molded under pressure to the form of a. stick,tube, pellet, button, washer, &c., and then, while surrounded by aneutral or reducing gas .or substance (6. g. water-gas, coal-gas, orplumbago in the pulverulent form) heated in an electric or othersuitable furnace until the particles of the carbid or carbids of themetal or metals of lower melting point become reduced to the partiallyor fullymolten state and envelop, weld or fuse together the particles ofcarbid or carbids of metals or metalloids of higher melting point, thusproducing. when the material has become cold, a hard, homogeneous masspossessing constant specific electrlcal resistance throughout.

The specific electrical resistance of the ma-- terial obtained may bevaried between wide limits either by making a selection of the carbidsand permanent binding substance or substances according to theirspecific electrical resistance or by varying the relative proportions ofthe carbids or of the permanent substance or both.

For example, a material containing only a small quantity of a carbid ofa metal or a carbid of a metalloid of high melting point and highspecific resistance and a relatively large amount of carbid of a metalof low melting point and low specific resistance would possess lowerspecific electrical resistance than a material containing a greaterproportion of the carbid of a metal or a carbid of a metalloid of highmelting point and high specific resistance.

In making a resistance material for use in electric motor starterstrollers, the following proportions adopted suitable or conmay be Boroncarbid 6 parts by weight.

Iron carbid 2 parts by weight. Neutral feldspari parts by weight.Glycerin ..1 part by weight.

What I claim is 1. An electrical resistance material comprising apartially fused mixture of a com-. pound of carbon and an element, saidelement having a melting point greater than 1500 C. and of a secondcompound of carbon and an element, said element having a melting pointbetween 1500 C. and 800 C.

2. An electrical resistance material comprising a partially fusedmixture of a compound of carbon and an element, said element having ameltin point greater than 1500 C. and of a second compound of carbon andan element, said element having a melting point between 1500 C. and 800C. the former material having a high specific resistance and the lattermaterial a relatively lower specific resistance.

3. An electrical resistance material comprising a partiall fused mixtureof two compounds each 0 carbon with an element, said elements havingrespectively a high specific resistance with a melting point above 1500C. and a relatively lower specific resistance with a melting pointbetween 1500 C. and 800 C. and a third permanent inert substance whichis neutral to each of the aforesaid compounds and has a melting pointless than that of either of them.

4:. An electrical resistance material comprising a mixture of boroncarbid, iron carbid and neutral feldspar.

CHARLES RUZICKA.

Witnesses:

HERBERT D. J AMESON, WILLIAM E. Rooms.

